Major histocompatibility complex and inflammatory cell subtype expression in inflammatory myopathies and muscular dystrophies.

ABSTRACT

BACKGROUND: In inflammatory myopathies muscle biopsy is a crucial diagnostic test. Misinterpretation between inflammatory myopathies and muscular dystrophies with inflammation is known. MATERIALS AND METHODS: Thirty-one patients clinically and pathologically diagnosed to have polymyositis and dermatomyositis and 16 patients of muscular dystrophy with inflammation were studied for MHC-I, MHC-II, CD4 and CD8 expression in skeletal muscle tissue. RESULTS: MHC-I upregulation was noted in all samples of PM and DM. Interstitial and perivascular inflammation in PM were predominantly CD8+ cells, in dermatomyositis, interstitial and perimysial perivascular inflammatory cells were CD4+ T cells and CD8+ T cells were seen around endomysial vessels. Interestingly MHC-I upregulation was seen in all 16 cases of muscular dystrophy with presence of inflammation. CONCLUSION: The pattern of MHC-I and II expression appeared to be similar in both inflammatory myopathies as well as in muscular dystrophies with inflammation and hence differentiating them on MHC - I expression was difficult.